We had this exact experience switching from a very small gym to a mega gym. The absolute hardest part has been our misguided thinking that everyone at all levels went there to "be serious" (for lack of better phrasing) when in reality there are just as many who ended up there based on geography alone. It's easy to tell the difference now (I hear a lot of "I would never drive that far", etc.) but was a definite shock at first.
As far as most of the other comments, I find the owner to be easily accessible, but that may be unique to our gym. She also knows every athlete in her gym, which astounds me! It's the coaches that aren't as accessible to parents. I worked in my CP's old gym and, frankly, it is a good thing when coaches aren't chatting it up with parents nonstop (exception: private lessons, of course). There seems to be a lot less favoritism and what I call "roll casting" in the larger gym too. They don't decide you are a flyer/base/backspot when you walk in the door and cast you in that roll until the end of time. You may fly one season and base the next. Crossovers often fly on one team and base on another.
Overall, it was the best decision for us. I've watched a new, more confident athlete who speaks up for herself & her team emerge from a shy wallflower.